Effects of Strength and Orientation of Steel Fiber on the Fracture Behavior of Steel Fiber Reinforced Concrete

各种纤维增强混凝土已被调查。它们的纤维直径通常为微米级。钢纤维混凝土中钢纤维的直径为0.1- 1.0mm，其力学性能与普通混凝土相似。本文研究了砂浆中钢纤维的强度和取向对钢纤维砂浆弹性模量和断裂强度的影响。所用的钢纤维是“SHINKO-钢纤维”，其标称尺寸为直径0.6 mm，长度30 mm，抗拉强度大于100 kgf/mm^2。还使用具有其它尺寸和强度的各种纤维。试样尺寸为40 × 40 × 160 mm ^3，老化28天以上后进行试验。结果表明：（1）SF的加入量即使在1wt%时，也能抑制裂纹的扩展.但SF对增强的贡献量大于5wt%。（2）SF的掺入会使弹性模量降低，但通过掺入适量的膨胀水泥，可以控制弹性模量的降低。（3）润滑SF不利于强化。（4）直径为10 μ m或长度为10 mm的SFs作用较小。（5）纵向取向的SF能有效地起到加固作用。（6）经180 ℃高温高压处理后，弹性模量降低。

Various fiber reinforced concretes have been investigated. Their fibers have usually micro-meter order in diameter. Exceptionally, the diameter of steel fiber in SFRC is 0.1-1.0 mm. Therefore, the mechanical behaviors seems to be similar to those of RC.In this investigation, the effects of strength and orientation of steel fiber in mortar on the modulus of elasticity and facture strength of steel fiber reinforced mortar (SFRM) have been studied. The steel fiber used is "SHINKO-steel fiber", whose nominal dimensions are 0.6 mm in dia, 30 mm in length and more than 100 kgf/mm^2 in tensile strength. Various kinds of fibers having other sizes and strengths were also used. The size of specimen was 40X40X160 mm^3, and after aging for more than 28 days, tests were carried out. Results obtained are as follows : (1)Even 1 wt% addition, SF suppress the propergation of cracks. But the amount of SF contributing to strengthening is more than 5wt%. (2)The modulus of elasticity decreases by addition of SF, but by the mixing of optimum amount of expand cement, the decreasing can be controlled. (3)Greased SF dose not contribute to strengthening. (4)The role of SFs having 10 micr-meter in diameter or having 10mm in lengthare small. (5)The longitudinally oliented SF can contribute to strengthening effectively. (6)The modulus of elasticity decreased after autoclave-treatment at 180 ﾟC.